pku3668 Game of Lines

http://poj.org/problem?id=3668

水题，STL

 #include <stdio.h>
 #include <set>

 using namespace std;

 set<pair<int, int> > set1;

 int gcd(int x, int y)
 {
     return y? gcd(y, x%y): x;
 }

 int abs(int x)
 {
     return x<? -*x: x;
 }

 struct P
 {
     int x, y;
 }p[];

 int main()
 {
     int n, i, j;
     int x, y, gcd_xy;
     while(~scanf("%d", &n))
     {
         set1.clear();
         for(i=; i<=n; i++)
         {
             scanf("%d%d", &p[i].x, &p[i].y);
         }
         for(i=; i<=n-; i++)
         {
             for(j=i+; j<=n; j++)
             {
                 x = p[i].x - p[j].x;
                 y = p[i].y - p[j].y;
                 if(x < )
                 {
                     x *= -;
                     y *= -;
                 }
                 gcd_xy = gcd(abs(x), abs(y));
                 x /= gcd_xy;
                 y /= gcd_xy;
                 if(x == )
                 {
                     y = ;
                 }
                 if(y == )
                 {
                     x = ;
                 }
                 //printf("%d %d : %d %d\n", i, j, x, y);
                 set1.insert(make_pair(x, y));
             }
         }
         printf("%d\n", (int)set1.size());
     }
     return ;
 }